1. Technical Field
The invention relates generally to methods and apparatuses for biological processing systems. More specifically, the invention relates to dispensers with filter devices.
2. Description of the Related Art
Automated biological processing systems can process samples for immunostaining and in situ DNA analysis. Immunostaining and in situ DNA analysis are useful tools in histological diagnosis and the study of tissue morphology. Immunostaining relies on the specific binding affinity of antibodies with epitopes in tissue samples, and the increasing availability of antibodies which bind specifically with unique epitopes present only in certain types of diseased cellular tissue, immunostaining involves delivering a series of substances to a tissue section mounted on a glass slide to highlight, by selective staining, certain morphological indicators of disease states. Typical processing steps include pretreatment of the tissue section to reduce non-specific binding, antibody treatment and incubation, enzyme labeled secondary antibody treatment and incubation, substrate reaction with the enzyme to produce a fluorophore or chromophore highlighting areas of the tissue section having epitopes binding with the antibody, counterstaining, and the like. A secondary anti-antibody can bind to the primary antibody that also includes a signal generating moiety such as an enzyme (for example, horseradish peroxidase or alkaline phosphatase) conjugated thereto. A combination of antibody conjugates that specifically bind the primary and the secondary antibodies is applied to the specimen. A DAB regent (e.g., diaminobenzidine (DAB)/hydrogen peroxide solution) is contacted to the specimen and allowed to incubate, during which time enzymes of the secondary antibody conjugate converts the soluble DAB into an insoluble brown precipitate at the sites where the primary antibody is specifically bound. The specimen is washed with buffer, followed by one or more rinses with ethanol, and one or more rinses with limonene to ready the specimen for subsequent processing, such as coverslipping.
Conventional automated biological processing systems often include dispensers that sequentially deliver fluids onto specimens. The dispensers can selectively dispense predetermined volumes of reagent. If solid particles (e.g., contaminates precipitates, or the like) are present in the fluid held in the dispensers, the solid particles may lead to impaired performance of the dispenser valving which results in improper dispensing. By way of example, if large precipitates form in a stored reagent, the precipitates can prevent complete closing of a valve. Conventional dispensers often hold precipitate forming solutions that tend to contain relative large precipitates (e.g., solid particles with diameters equal to or larger than about 0.01 inch), especially if the dispenser is stored for extended periods of time.